Hydrogen sulfide (H2S) and carbon dioxide (CO2) are commonly found together in gases and liquids in the energy production and chemical industries. These gases include hydrocarbon gases synthesized from coal, petroleum coke, residual oils, shale oil, tar sands, biomass, and other carbonaceous materials. Hydrogen sulfide is poisonous and considered a pollutant that contributes to acid rain. Therefore, hydrogen sulfide must be prevented from escaping into the atmosphere. Common methods for removing hydrogen sulfide from a liquid or gas include scrubbing with either a physical solvent, such as SELEXOL®, an alkaline solvent, such as solutions of amine, or inorganic bases, such as sodium hydroxide and direct liquid oxidation technologies like SULFEROX® and LOCAT®. Unfortunately, carbon dioxide is also soluble in most physical solvents and has a greater affinity for alkaline solvents than hydrogen sulfide. The carbon dioxide competes with the hydrogen sulfide for the solvent, requiring increased solvent circulation rates and regeneration energy to remove the hydrogen sulfide. Therefore, the presence of carbon dioxide greatly increases the expense of removing hydrogen sulfide from a mixture.
In addition to hydrogen sulfide and carbon dioxide, ammonia (NH3) is also frequently found in gases and liquids of the energy production and chemical industries. Like hydrogen sulfide, ammonia must be separated and contained to prevent its release. The separation of ammonia from liquids and gases is often performed by washing with water. The ammonia and hydrogen sulfide solublized in the water are then separated from the water by distillation in a sour water stripper, producing an off gas comprising ammonia. Disposing of ammonia can be both expensive and dangerous.